CYP2D6 Testing Could Ease Parents Fears After Codeine Warning

A recent warning from the American Academy of Pediatrics has many parents worrying if their child is an ultrarapid metabolizer of the popular drug codeine. The clinical report is calling for a formal restriction of codeine, over risks of life-threatening or fatal breathing reactions. The pain reliever is often given in hospitals for procedures such as tonsillectomies and is commonly prescribed as a cough suppressant.

Codeine is a prodrug, meaning that it is taken in an inactive form and then converted to the active form in the body. In this instance, codeine is converted to morphine by the liver enzyme CYP2D6 which is highly influenced by genetic variability. If a child is an ultrarapid CYP2D6 metabolizer, the drug turns into a dangerously high level of morphine in their blood, possibly causing life-threatening or fatal reactions. The FDA has issued a black box warning about codeine, specifically citing the role of DNA variations of CYP2D6 which can have a significant impact on treatment outcome.

To keep children safe, the AAP report calls for parent education in addition to restricting the use of codeine. Many parents have turned to pharmacogenetics to remove the guesswork of how their child’s genetic variability will play into the outcome of drugs like codeine. A simple cheek swab test analyzing CYP2D6 could ease many parents’ worst fears by determining how codeine would potentially process through their child’s body.

Nursing mothers need to also be aware of life-threatening side effects in the baby. Though codeine is generally considered to be compatible with breastfeeding, it is possible for codeine to affect breast milk and harm a nursing baby. If a mother is a CYP2D6 ultrarapid metabolizer, codeine would be converted into morphine in her body at a much faster rate (compared to a normal metabolizer), which can very quickly lead to toxicity and overdose. Click here to read the story of a Seattle mom who used her YouScript results to protect her baby shortly after birth.

The AAP report also breaks down the frequency of the ultrarapid metabolizer genotype, “estimated at ∼29% of patients of African/Ethiopian heritage, ∼21% of those from Saudi Arabia and other Middle Eastern countries, and ∼3.4% to 6.5% of African-American and white persons.” Although the percentages do not make up the majority of children, it is worth noting the value of pharmacogenetics here. CYP2D6 testing could help make the effects of codeine more predictable, and restore a parent’s peace of mind.